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•1 <br />+ - III IIIIIIIIIIIII III <br />,~ ~" sss <br />.x <br />L'; h;. <br />''~x', - <br />`,r ~~. <br />Lincoln DeVore,lnc. <br />- Geotechnical Consultants <br />1441 Motor St. TEL: (303) 242-8968 <br />Grand Junction, CO 81505 FAX: (303) 242-1561 <br />September 25, 1995 <br />Mr. hurt Sheppard <br />KLH Engineering <br />2576 Foresight Circle, #9 <br />Grand Junction, CO 81505 <br />RE: Slope Stability for Reclamation <br />O.C. Mine #2, Gunnison County, Colorado <br />Gentlemen; <br />At your r•egtrest, personnel of this office have performed direct <br />shear strength tests on bulk samples delivered to this office by <br />personnel of KLH Engineering. In addition, personnel of Lincoln <br />DeVore have performed Slope Stability Analysis of existing slopes <br />at the O.C. #2 Coal Mine, in anticipation of reclamation pro- <br />jects. Following are our findings. <br />Two bulk samples were delivered to Lincoln DeVore for testing, in <br />addition, thirteen bulk moisture samples and three hand-driven <br />Shelby tuhes were delivered. These samples were tested for in- <br />place moisture content, the Shelby tubes for in-place soil densi- <br />ty and all samples were visually classified & grouped with the <br />two large bulk samples. Based upon the samples delivered to <br />Lincoln DeVore, the clayey gravel of bulk sample S-1 was utilized <br />for shear strength testing and the analysis of the in-place slope <br />stability of both man-made fill slopes and man-made cut slopes. <br />A Slope Stability Analysis was performed using the computer <br />program GEOSI,OPE version 4.0 by GeoComp Corporation, based upon <br />tfre Fortran program STABL4. Tiie method of analysis is the Sim- <br />plified Jambii hfethod of Slices with Irregular Failure Surfaces. <br />The Factors i' Safety were computed using the Modified Bishop <br />Method. <br />The site and slope geometry applied to this analysis was taken <br />from the topography map of O.C. Coal Mine #2 by Ki,H Engineering <br />Group, 9-14-95. <br />Based upon the mapped ground topography and several possible <br />reclamation schemes, the critical section was found to be the <br />overfill of coal waste of Section D-D'. A piezometric surface <br />was not assumed in the calculations. The soils were assumed to <br />be nearly saturated due to seasonal snowmelt. A pseudostatic <br />form of 0.058 (horizontal) was assumed as an earthquake coeffi- <br />d <br />i <br />